Not Applicable
Not Applicable
The present invention relates to ultrasound cleaning systems, and more particularly, to systems, generators and methods that clean and/or process by coupling multiple frequency sound waves into a liquid to optimize cleaning performance. This application is related to the following U.S. Patents, which are hereby incorporated by reference: U.S. Pat. No. 5,834,871, Apparatus and Methods for Cleaning and/or Processing Delicate Parts, issued Nov. 10, 1998; U.S. Pat. No. 6,002,195, Apparatus and Methods for Cleaning and/or Processing Delicate Parts, issued Dec. 14, 1999; and, U.S. Pat. No. 6,016,821, Systems and Methods for Ultrasonically Processing Delicate Parts, issued Jan. 25, 2000.
There is a 40 year history of multiple frequency cleaning or processing systems. These systems can be organized into several classes of equipment. The first class of equipment consists of a tank holding liquid with two or more transducers (or two or more transducer arrays) that couple sound energy into the tank and each of these transducers (or arrays) is driven by a different generator. Typically all the generators are operated at the same time or there is an overlap in the operating times of the generators so that two or more frequencies are simultaneously put into the tank for at least part of the cleaning or processing cycle. The chronological history of this first class of equipment starts in 1959 with U.S. Pat. No. 2,891,176 where Branson teaches three transducer arrays driven by three generators, the operation periods of these generators overlap in a way to balance the current in a transformer. In 1974 a tank was designed and built at Branson Cleaning Equipment Company that had an array of 25 kHz transducers on the bottom and a second array of 40 kHz transducers on one side; each of these arrays was simultaneously driven by the appropriate frequency generator. Similar systems were designed and built by others in the 1970""s, e.g., Blackstone, but no useful application was found for the technology. In 1981 U.K. Pat. No. 2,097,890A taught three transducer arrays driven by three generators on different phases of a three-phase line. In the mid 1990""s Amerimade Technology sold a system consisting of a tank with angled walls and two arrays of transducers on different walls, each array was driven by a different frequency generator, one sweeping around 71.5 kHz and the other sweeping around 104 kHz. At around the same period in time, Zenith sold a two array two generator system operating at 80 kHz and 120 kHz called xe2x80x9ccrossfirexe2x80x9d because the different frequencies intersected at 90 degrees. Unlike the earlier 25 kHz and 40 kHz systems that found no useful application, the personal computer industry now existed and these Amerimade and Zenith systems were sold in large volume to the hard disk drive industry. In U.S. Pat. No. 5,656,095 Honda, et al. teaches high frequency transducers and low frequency transducers on the tank where the high frequency transducers are normally driven and the low frequency transducers are driven for short periods of time to intermittently destroy the high frequency bubbles. In U.S. Pat. No. 5,865,199 Pedziwatr et al. teaches two arrays of transducers interspersed on the tank and driven by two different frequency generators. In U.S. Pat. No. 5,909,741 Ferrell teaches two arrays of transducers on different angled walls of a plastic container and driven by different frequency generators.
A second class of multiple frequency cleaning equipment has one array of multiple frequency transducers that couple sound into the liquid in the tank and this array is driven by a pulse or square wave generator or some other form of shock excitation where the generator output is rich in harmonic frequencies or produces a number of integral harmonic frequencies. Multiple resonances in the multiple frequency transducer array are excited by the appropriate harmonics in the generator""s output. Therefore, multiple frequencies are simultaneously coupled into the tank from a single transducer array and a single generator or multiple frequencies are combined in the tank. In U.S. Pat. No. 3,315,102 Quint et al. teaches driving a tank with simultaneous multiple frequencies through shock excitation from a spark gap generator. In U.S. Pat. No. 3,371,233 Cook teaches shock excitation of a non-symmetrical transducer to simultaneously produce many frequencies in a tank. U.K. Pat. No. 1,331,100 teaches a non-symmetrical transducer that can simultaneously vibrate at a number of different frequencies and harmonics of these frequencies. When driven by a generator with a harmonic rich output, this transducer will produce simultaneous multiple frequencies. Other transducers capable of multiple frequencies are taught by Thompson and by Goodson in U.S. Pat. Nos. 4,633,119 and 5,748,566 respectively. In U.S. Pat. No. 5,076,854 Honda, et al. teaches that rapid switching to different frequencies shocks the transducer into producing multi-frequencies in between the drive frequencies. In U.S. Pat. No. 5,462,604 Shibano et al. teaches a way to effectively produce square wave drive characteristics in the liquid by driving the transducer with odd integer multiples of the natural resonant frequency of the transducer. One disadvantage to this class of cleaning equipment is that often the resonant frequencies of the resonantor do not correspond with the harmonic peaks of the driving generator, resulting in less than optimum performance from the cleaning equipment.
A third class of multiple frequency cleaning equipment has multiple transducers (or multiple arrays of transducers), each transducer (or array) having a different frequency and a generator with multiple outputs, each output having a different frequency matched to the transducer (or array) to which it is connected. In U.S. Pat. No. 2,985,003 Gelfand et al. teaches a system where the generator can supply a number of single frequencies to the same number of transducers to set up that number of different standing wave patterns. In U.S. Pat. No. 3,746,897 Karatjas teaches a generator that is capable of supplying an integer number of different single frequencies. One specific single frequency is chosen by a switch for operation. Each specific single frequency drives a different transducer designed to operate at that specific frequency.
One disadvantage common to the above-described configurations is that often the intensity of the ultrasound delivered to the component being cleaned is insufficient for the particular, desired cleaning task.
It is an object of the present invention to substantially overcome the above-identified disadvantages and drawbacks of the prior art.
The multiple frequency invention described herein is a new class of liquid cleaning and processing equipment where there is one transducer array and one generator that produces a series string of different frequencies within two or more non-overlapping continuous frequency ranges. The transducer array is capable of responding to electrical frequency signals to produce intense sound energy at any frequency within two or more distinct frequency bands. The generator is capable of supplying an electrical frequency signal at any frequency within continuous frequency ranges contained within two or more of the transducer array""s frequency bands.
The generator and transducer array produce a series string of different frequency sound waves. The first produced frequency is typically followed by a different second frequency that is in the same frequency range as the first frequency, then this second frequency is typically followed by a different third frequency that is in the same frequency range as the first two frequencies, and this pattern continues for at least the lifetime of a sound wave in the liquid (typically 20 to 70 milliseconds). This results in multiple closely related frequencies of the same frequency range adding up within the liquid to a value of high intensity sound. This high intensity multiple frequency sound field is typically maintained long enough to accomplish a specific part of the cleaning or processing cycle, then the electrical frequency signal output of the generator is controlled to jump to a frequency in a different frequency range, typically in a different frequency band, where different frequencies are again strung together for at least the lifetime of a sound wave in the liquid.
This invention is an improvement over prior art multiple frequency systems because by stringing together different frequencies from the same frequency range for at least the lifetime of a sound wave in the liquid, the sound intensity of these closely related frequencies builds up to a higher value than with any of the prior art multiple frequency systems. This higher intensity sound field does the improved cleaning or processing within the frequency range and then the system jumps to another frequency range where the cleaning or processing effect is different. Again, in the second frequency range the sound intensity builds up to a higher value than with any prior art multiple frequency system and, therefore, the improvement in cleaning or processing occurs within this second frequency range. Also, by maintaining the production of sound in each frequency range for a minimum of 20 milliseconds, there is substantially no intense sound energy produced at frequencies outside of the frequency ranges, this further adds to the build up of the intensity of the sound energy. Each of these improved effects in each of the different frequency ranges adds up to a process that is superior to prior art methods.
A variation of the invention substitutes a fraction of a cycle of a frequency strung together with other fractions of a cycle of sound at different frequencies within a given frequency range before jumping to a different frequency range. Another variation inserts a degas time between jumps from one frequency range to another. Another variation controls the generator to cycle through the frequency ranges in different orders, i.e., several permutations of the frequency ranges are introduced into the liquid during the cleaning or processing cycle. Another variation defines each permutation of a frequency range to be a cleaning packet and the order in which these cleaning packets are delivered to the liquid is varied to produce different cleaning effects. Still other variations introduce phase lock loops, duty cycle control, amplitude control, PLC control, computer control, quiet times, active power control, series resistor VCO control, DAC VCO control, cavitation probe feedback to the generator and digital code frequency selection. In general, this invention is useful in the frequency spectrum 9 kHz to 5 MHz.
The foregoing and other objects of are achieved by the invention, which in one aspect comprises a system for coupling sound energy to a liquid, including at least two transducers forming a transducer array adapted for coupling to a liquid in a container. The transducer array is constructed and arranged so as to be capable of producing intense sound energy in the liquid at any frequency within at least two non-overlapping frequency bands. The system further includes a signal generator adapted for producing a driver signal for driving the transducer array at any frequency from one or more continuous frequency ranges within each of at least two frequency bands. The signal generator drives the transducer array to produce the intense sound energy characterized by a series string of different frequencies within one of the continuous frequency ranges. The generator further drives the transducer array to discontinuously jump amongst the frequency ranges, so as to generate intense sound energy characterized by a series string of different frequencies within at least one additional frequency range in at least one additional frequency band.
Another embodiment of the invention further includes a controller for controlling the frequency of the ultrasonic energy within the series string of different frequencies. The controller also controls a duration of each frequency in the series string.
In another embodiment of the invention, the intense sound energy in the series string of different frequencies is characterized by a staircase function.
In another embodiment of the invention, the intense sound energy in the series string of different frequencies is characterized by a series of monotonically decreasing frequencies.
In another embodiment of the invention, the series of monotonically decreasing frequencies occurs for at least ninety percent of an interval during which the transducer array couples intense sound energy to the liquid.
In another embodiment of the invention, the intense sound energy in the series string of different frequencies is characterized by a series of frequencies defined by a predetermined function of time.
In another embodiment of the invention, the intense sound energy in the series string of different frequencies is characterized by a series of frequencies swept from a first frequency to a second frequency at a constant sweep rate.
In another embodiment of the invention, the series of frequencies is swept at a non-constant sweep rate.
In another embodiment of the invention, the intense sound energy in the series string of different frequencies is characterized by a random series of frequencies.
In another embodiment of the invention, the intense sound energy in the series string of different frequencies is characterized by at least a first group of frequencies from a first frequency band, and a second group of frequencies from a second frequency band, such that at least two groups of frequencies adjacent in time are from different frequency bands.
In another embodiment of the invention, the series string of different frequencies further includes at least one degas interval between periods of time having ultrasonic energy.
In another embodiment of the invention, the intense sound energy in the series string of different frequencies is characterized by at least a first group of frequencies from a first frequency band, and a second group of frequencies also from the first frequency band, such that at least two groups of frequencies adjacent in time are from the same frequency band
In another embodiment of the invention, the intense sound energy in each of the series string of different frequencies is characterized by at least a fraction of a cycle of the distinct frequency.
In another embodiment of the invention, the fraction of a cycle is one-half of a cycle, and each successive one-half cycle represents a different frequency.
In another embodiment of the invention, the intense sound energy includes frequencies selected from the frequency spectrum 9 kHz to 5 MHz.
In another embodiment of the invention, the frequency ranges are characterized by a center frequency. The center frequency of each higher frequency range is a non-integer multiple of the center frequency of the lowest frequency range, so as to prevent one or more Fourier frequencies of a periodic wave from forming in the liquid.
In another embodiment of the invention, the controller includes a PLC or a computer.
Another embodiment of the invention further includes a probe adapted for measuring one or more parameters associated with the liquid corresponding to sound-produced effects in the liquid. The controller alters the generator driver signal as both a predetermined function of the measured parameters, and according to the desired purpose of the system.
In another embodiment of the invention, each specific frequency range is represented by a distinct digital code. The controller initiates a transition from a first frequency range to a second frequency range in response to the digital code transitioning from a digital code representative of the first frequency range to the digital code representative of the second frequency range.
In another embodiment of the invention, the center frequency of each frequency range corresponds to an output of a voltage controlled oscillator. The output of the voltage controlled oscillator corresponds to an input control signal, and the input control signal is determined by a series string of resistors. The total string of resistors produces the lowest frequency range and each higher string of resistors produces each higher frequency range.
In another embodiment of the invention, the intense sound energy includes ultrasonic energy.
In another embodiment of the invention, the intense sound energy in the series string of different frequencies occurs continuously for at least 20 milliseconds, within each of the continuous frequency ranges.
In another embodiment of the invention, the output power level of the driver signal is actively maintained by comparing an actual output power level to a specified output power level, and adjusting parameters of the driver signal to make the actual output power level substantially equal to the specified output power level. The parameters of the driver signal may be either amplitude, duty cycle, or some combination thereof.
In another embodiment of the invention, the intense sound energy characterized by the series string of different frequencies further includes one or more quiet time intervals characterized by a substantial absence of intense sound energy.
In another embodiment of the invention, the quiet time intervals are distributed periodically among the intervals of intense sound energy. In yet another embodiment, the quiet time intervals are distributed randomly among the intervals of intense sound energy.
In another embodiment of the invention, the quiet time intervals are distributed among the intervals of intense sound energy according to a predetermined function of time.
In another embodiment of the invention, the center frequency for each frequency range is optimized by an automatic adjustment from a circuit that maintains a substantially zero phase shift between an associated output voltage and output current at the center frequency.
In another embodiment of the invention, the order of frequency range transitions varies such that several permutations of frequency ranges can be introduced into the liquid. In other embodiments, each permutation of frequency ranges is defined as a specific cleaning packet, and the order in which the cleaning packets are introduced into the liquid is changed such that each different order produces a different cleaning effect.
In another embodiment of the invention, substantially no intense sound energy is produced at frequencies outside of the frequency ranges.
In another embodiment of the invention, the container holding the liquid is constructed from materials resistant to detrimental effects of the liquids. These materials may include tantalum, polyetheretherketone, titanium, polypropylene, Teflon, Teflon coated stainless steel, or combinations thereof, or other similar materials known to those in the art.
In another embodiment of the invention, the signal generator is capable of producing any of an infinite number of frequencies contained within each of the unconnected continuous frequency ranges.
In another embodiment of the invention, the signal generator produces an output signal including the FM information for synchronizing other generators or power modules.
In another embodiment of the invention, the center frequency of each frequency range corresponds to an output of a voltage controlled oscillator. The output of the voltage controlled oscillator corresponds to an input control signal, and the input control signal is generated by a DAC (digital-to-analog converter). In other embodiments, the digital input to the DAC produces a stepped staircase analog output from the DAC, resulting in a stepped, staircase sweeping function within a frequency range. In yet another embodiment, the digital input to the DAC produces a random staircase analog output from the DAC, resulting in a random staircase sweeping function within a frequency range.
In another aspect, the invention comprises a system for coupling sound energy to a liquid. The system includes at least two transducers forming a transducer array adapted for coupling to a liquid in a tank, and the transducer array is constructed and arranged so as to be capable of producing intense sound energy in the liquid at any frequency within at least two non-overlapping frequency bands. The system further includes a signal generator adapted for producing a driver signal for driving the transducer array at any frequency from one or more continuous frequency ranges within each of the at least two frequency bands. The signal generator drives the transducer array so as to produce intense sound energy characterized by a plurality of changing frequencies within a first frequency range, followed by a plurality of changing frequencies within a second frequency range. The system so operating reduces a strong antinode below the liquid-to-air interface.
In another aspect, the invention comprises a system for coupling sound energy to a liquid, that includes at least two transducers forming a transducer array adapted for coupling to a liquid in a tank. The transducer array is constructed and arranged so as to be capable of producing intense sound energy in the liquid at any frequency within at least two distinct frequency bands. The system further includes a signal generator adapted for producing a driver signal for driving the transducer array at any frequency from one or more continuous frequency ranges within each of the at least two frequency bands. The center frequencies of the higher frequency ranges are non-integer multiples of the center frequency of the lowest frequency range to prevent two or more Fourier frequencies of a periodic wave from forming in the liquid. The signal generator drives the transducer array to produce sound energy corresponding to a first set of frequencies from a first frequency range, then produces sound energy corresponding to a second set of frequencies from a second frequency range. The transition from the first frequency range to the second frequency range is discontinuous and occurs after a time interval at least as long as the lifetime of sound energy in the container for frequencies from the first frequency range. The sound energy corresponding to the second set of frequencies continues for a time interval at least as long as the lifetime of sound energy in the container for frequencies from the second frequency range.
In another aspect, the invention comprises multiple frequency generator capable of producing an output signal characterized by any frequency within two or more non-contiguous, continuous frequency ranges. The generator is controlled to change the frequency within a frequency range, and then to change frequencies from one frequency range to a second frequency range before beginning the changing of frequencies in this second frequency range.
In another aspect, the invention comprises a method of delivering multiple frequencies of intense sound waves to a liquid. The method includes the step of coupling to the liquid an array of transducers that are capable of producing sound energy in the liquid at an infinite number of different frequencies contained within two or more non-contiguous, continuous frequency bands. The method also includes the step of driving the transducer array with a generator capable of producing substantially all of the frequencies within continuous frequency ranges contained within two or more of the transducer array frequency bands. The method further includes the step of controlling the generator so that the produced frequencies change within the frequency ranges according to a function of time, and the frequencies jump amongst the frequency ranges.